The present invention relates to a method for manufacturing a liquid crystal cell, and more particularly to a method for manufacturing a twisted nematic(referred as TN) liquid crystal cell using an ultraviolet light irradiated an alignment layer to make two domains in each pixel, that is, each domain has a different alignment direction. Thereby, the viewing angle compensates each other so as to provide a wider viewing angle without grayscale-reversal problem.
It is well known that the TN LCD, which is now most commonly employed, has a narrow and non-uniform viewing angle causing changing a transmittance in the gray level FIG. 1a is showing the relation between the transmittance of LC cell and a voltage, FIG. 1b is showing the relation between the viewing angle in the horizontal direction and the transmittance, and FIG. 1c is showing the relation between the viewing angle in the vertical direction and transmittance. Particularly, referring to FIG. 1, while it is a symmetric transmittance between right and left viewing angle, it is asymmetric transmittance between upper and lower viewing angle. The viewing angle gets narrower because an image inversion occurs between an upper and lower viewing angle. To overcome this problem of the narrow viewing angle, two major approaches have been proposed i.e., a multi-domain TN LCD such as a two-domain TN LCD, a domain-divided TN LCD and a four-domain TN LCD, and an optical compensation using two retardation films compensated birefringence mode LCD. Referring to a structure of LC cell in FIG. 2, each pixel has two-director configuration, wherein the two directors are in the opposite direction. Applying a gray level voltage to this cell, the LC directors are tilted in opposite directions, thereby, two domains is obtained. The two-domain TN LC cell is made by the following steps: rubbing the entire alignment layer 2 coated on a substrate 1 in the first rubbing direction; making mask to block one domain by a photoresist; rubbing the other domain at the reverse direction to the first rubbing direction; and removing said photoresist. Thereby, it obtains two liquid crystal directors which are in opposite directions in each pixel.
Referring to domain-divided LC cell in FIG. 3, the alignment layers 12,13 consist of two materials having different pretilt angles. The first alignment layer 12 is organic and the second alignment layer 13 is inorganic.
According to the reverse rubbing process in FIG. 4, the polyimide 22 coated substrate 21 is rubbed in the first rubbing direction, then photoresist 23 as a mask is formed on some area of the substrate 21. Then other area of the substrate 21 is rubbed in the opposite direction to the first rubbing direction and finally, the photoresist 23 is removed.
For the double SiOx oblique evaporation in FIG. 5, SiOx is evaporating the substrate with some angle, the photoresist is formed to divide a pixel. Then SiOx is evaporating in the opposite direction to the previous evaporating direction on the substrate 21 and the photoresist 23 used as a mask is removed. Thereby, two domains having the different pretilt angle each other are provided.
However, the two-domain TN and the domain-divided TN are fabricated through the rubbing process and photolithography process so the process becomes very complicated, also a particle and an electrostatic discharge are generated during the rubbing process. Therefore, the yield is decreased, or liquid crystal gets damaged.